1. Field of the Invention
The present invention relates to a liquefied natural gas (LNG) storage container and a method for manufacturing the same, and more particularly, to an LNG storage container, which is capable of efficiently storing LNG or pressurized LNG (PLNG) pressurized at a predetermined pressure and supplying the LNG or PLNG to a consumption place, capable of reducing manufacturing costs by minimizing the use of a metal having excellent low temperature characteristic, and has an inner shell having high-efficiency heat insulation performance, and a method for manufacturing the same.
2. Description of the Related Art
In general, liquefied natural gas (LNG) is a cryogenic liquid produced by cooling natural gas (predominantly methane) to a cryogenic state of −162° C. at atmospheric pressure. The LNG takes up about 1/600th the volume of natural gas. The LNG is colorless and transparent. It has been known that the LNG is cost-efficient in terms of a long-distance transportation because of high transportation efficiency as compared to a gaseous state.
Since a large amount of cost is spent in the construction of production plants and the building of carriers, the LNG has been applied to a large-scale long-distance transportation in order for cost reduction. On the other hand, it has been known that a pipeline or compressed natural gas (CNG) is cost-efficient in terms of small-scale short-distance transportation. However, the transportation using the pipeline may have geographical restrictions and cause environmental pollution, and the CNG has low transportation efficiency.
A conventional method for distributing LNG to consumption places requires high costs and has difficulty in flexibly responding to various demands of consumption places. Also, since it is necessary to provide separate storage tanks at the consumption places, high infrastructure costs are needed and a lot of time and effort to unload LNG are needed.
In addition, natural gas has a liquefaction point of −163° C. at atmospheric pressure. If a predetermined pressure is applied, the liquefaction point of the natural gas further increases than at the atmospheric pressure. This characteristic may reduce processing steps in a liquefaction process, such as acid gas removal and natural gas liquid (NGL) fractionation. This leads to a reduction in facilities and facility capacity. Therefore, the LNG production costs may be reduced.
However, a conventional LNG storage tank installed in a vessel having a gasification facility or an LNG terminal has a limitation in size. In addition, it is unsuitable for cost-efficient storage of LNG while reflecting the above-described LNG characteristic. It is difficult to easily transport LNG to consumption places according to consumer's various demands.
In order to solve the above problems, a container for storing general LNG or PLNG may be made of a metal having excellent low temperature characteristic in order to withstand a high pressure and a cryogenic temperature of −120° C. or below. To this end, the thickness of the wall of the storage container is inevitably increased. Furthermore, since an expensive metal having excellent low temperature characteristic is used, it is difficult to ensure economic feasibility.